Video signal processor for removing a separated signal component from an input video signal

ABSTRACT

A video signal processor is used in connection with a television set or similar apparatus for processing a video signal input for every horizontal line period. A video signal is processed by operations such as comparison and addition of a video signal, a first delay signal which is delayed by a one-horizontal line period and a second delay signal which is delayed by a two-horizontal line period. Since there is a horizontal correlation in a video signal, it is possible to separate a color signal from a luminance signal and remove the noise component from the luminance signal by a predetermined operation. The comparison is substantially the subtraction of the signals which are output one after another by a delay of one horizontal line period in series, thereby avoiding such trouble as color edging.

This application is a divisional of copending application Ser. No.08/025,807, filed on Mar. 3, 1993, which is a continuation of priorapplication Ser. No. 07/605,391, filed Oct. 30, 1990, now abandoned, theentire contents of which are hereby incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a video signal processor and, moreparticularly, to a luminance signal and a color signal separatingcircuit, and a noise reducing circuit for a video signal.

2. Description of the Related Art

FIG. 15 is a block diagram of the circuit of what is called a combfilter which is generally used for a VTR, a TV set, etc. In the NTSCbroadcasting system, a color burst signal and a color signal areinverted before transmission for every horizontal line (about 63.5 μs,hereinunder referred to as "1H"), as shown in FIG. 18. Such a combfilter is utilized as a filter for separating a luminance signal (Ysignal) from a color signal (C signal). In a VTR, a comb filter isutilized as a filter for cancelling the crosstalk component in a colorsignal.

In FIG. 15, the reference numeral 100 represents a video signal. Thevideo signal 100 is input to a band pass filter 1 (hereinunder referredto as "BPF"), for transmitting only a band of frequencies in which thecolor signal component exists and a delay circuit 2. The output of theBPF 1 is input to a 1H-delay circuit 3 for delaying a signal by a 1Hperiod, and the output of the 1H-delay circuit 3 is input to asubtractor 4. The subtractor 4 subtracts the output of the 1H-subtractor3 from the output of the BPF 1. The output of the subtractor 4 is inputto a subtractor 6 as a C signal through a gain adjuster 5. Thesubtractor 6 generates a Y signal by subtracting the output (C signal)of the gain adjuster 5 from the output of the delay circuit 2.

The operation of this comb filter will now be explained. The operationsof the 1H-delay circuit 3 and the subtractor 4 will first be explained.Due to the above-described structure of the 1H-delay circuit 3 and thesubtractor 4, the transmission function in this part is represented asfollows: ##EQU1## Accordingly, ##EQU2##

From this equation, it is obvious that the frequency characteristic is afunction of a repeated reciprocal of T_(H). More specifically, thefrequency characteristic resembles the shape of the teeth of a combwhich has the maximum value when ##EQU3## (n is an integer) and theminimum value when f=n/T_(H).

In multiplexing a luminance signal and a color signal in the NTSCbroadcasting system, the frequency-division multiplex system whichutilizes frequency interleaving, as shown in FIG. 16, is adopted.Therefore, a color signal spectrum is distributed between every adjacentluminance signal spectra emitted at an interval of f_(h) (=1/T_(H)). Itis therefore possible to extract either the luminance signal spectrum orthe color signal spectrum emitted at an interval of f_(h) by using theabove-described comb filter composed of the 1H-delay circuit 3 and thesubtractor 4.

The BPF 1 is a filter for transmitting a band of frequencies in which acolor signal exists (e.g., 3.58 MH_(z) ±500 KH_(z) in the NTSC system),as shown in FIG. 17 The band of frequencies which are passed through theBPF 1 is set at a frequency band having a frequency characteristicresembling the shape of the teeth of a comb. The delay circuit 2 is afilter for compensating for the propagation delay of the BPF 1, thesubtractor 4 and the gain adjuster 5. By the delay circuit 2, the phaseof a video signal is adjusted and the gain adjuster 5 adjusts the gainof the color signal C which is extracted in accordance with thefrequency characteristic in the shape of the teeth of a comb and outputfrom the subtractor 4. The subtractor 6 removes the color signal C so asto generate the luminance signal Y.

The above-described comb filter, however, deteriorates the verticalresolution because the operation is carried out in the verticaldirection of the screen, which leads to the following defects in thepicture quality.

For example, video signals for producing a picture shown in FIG. 20(a)are shown in FIG. 18. In FIG. 18, the video signals before and after thevideo signal for the horizontal line n-th H on which a red color changesto a white color, as shown in FIG. 20(a), are shown. The signals outputbefore the signal for the n-th H transmit a color signal red and thesignals for the n-th H and therebelow transmit a color signal white.When these signals are input to the video processing circuit shown inFIG. 15, the video processing circuit outputs the signals such as thoseshown in FIG. 19. That is, on the n-th H, unnecessary signals arecontained in the Y signal and the C signal. When these signals areoutput on the TV screen, the picture shown in FIG. 20(b) is produced. Inother words, a phenomenon called color edging (red sags from theboundary line between red and white to the region of white) is producedon the line on the screen on which the color changes, or a phenomenoncalled dot disturbance (a signal of 3.58 MH.sub. z is mixed with aluminance signal) is produced.

Such a deterioration in the picture quality is a critical defect in aVTR. This is because color edging is produced not only in the luminancesignal and color signal separation in the interior of a VTR but also inthe horizontal correlative noise cancellation in the crosstalk cancellerin the VTR and in the luminance signal and color signal separation forthe VTR output signal carried out again in a TV and, as a result, coloredging is produced extending over several H's.

The luminance signal is also deteriorated in vertical resolution, asshown in FIG. 21, which shows the state of the picture in which theblack bar is sagging and is cut at the n-th H. The output of the BPF 1on the (n-1)th H only exists in the transient portions. When a videosignal for the n-th H is input, no output of the BPF 1 exists. However,since the 1H-delay circuit 3 supplies the output of the BPF 1, theunnecessary C and Y signals are output. The C signal and Y signal outputin spite of the absence of the output of the BPF 1 on the n-th H causescross color and the deterioration in the vertical resolution,respectively. In the picture displayed on the basis of the Y signal, ablack dot and a white peak appear, as shown in FIG. 21, whichdeteriorate the definition of the picture.

SUMMARY OF THE INVENTION

Accordingly, it is an object of the present invention to eliminate theabove-described problems in the related art and to provide a videosignal processor which is capable of reducing color edging, dotdisturbance, cross color and deterioration in vertical resolution.

To achieve this aim, a video signal processor according to the presentinvention has a delay circuit for delaying an input video signal by anintegral number of times the horizontal line period so as to generatetwo kinds of delay signals, namely, a first delay signal and a seconddelay signal. The video signal processor has the following structure soas to compare these three signals.

In the first aspect of the present invention, the video signal processorcomprises:

a maximum value calculator for comparing the video signal, the firstdelay signal and the second delay signal which are input thereto andoutputting the maximum value;

a minimum value calculator for comparing the video signal, the firstdelay signal and the second delay signal which are input thereto andoutputting the minimum value;

a synthesizer for outputting a signal obtained by subtracting theoutputs of the maximum value calculator and the minimum value calculatorfrom the sum of the video signal, the doubled first delay signal and thesecond delay signal; and

a subtractor for subtracting the output of the synthesizer from thefirst delay signal.

In the second aspect of the present invention, the video signalprocessor comprises:

a first synthesizer for compounding the antiphase video signal, thefirst delay signal and the second delay signal;

a second synthesizer for compounding the video signal and the seconddelay signal;

a third synthesizer for compounding the video signal, the doubled firstdelay signal and the antiphase second delay signal;

a maximum value calculator for comparing the output signals of thefirst, second and third synthesizers which are input thereto andoutputting the maximum value;

a minimum value calculator for comparing the output signals of thefirst, second and third synthesizers which are input thereto andoutputting the minimum value;

an adder for adding the output of the maximum value calculator and theoutput of the minimum value calculator; and

a subtractor for subtracting the output signal of the adder from thefirst delay signal.

In the third aspect of the present invention, the video signal processorcomprises:

a first adder for adding the video signal and the first delay signal;

a second adder for adding the doubled first delay signal and the seconddelay signal;

an intermediate value calculator for outputting the intermediate valueof the doubled first delay signal, the output of the first adder and theoutput of the second adder which are input thereto; and

a subtractor for subtracting the output signal of the intermediate valuecalculator from the first delay signal.

In the first aspect of the present invention,for example, when the videosignal for the (n-1)th H is input, the output of the synthesizercorresponds to the color signal at the (n-2)th H, and the colorcomponent in the Y component is cancelled by the output C. When thevideo signal for the (n+1)th H is input, neither the output Y or theoutput C is contained in the signal for the n-th H, thereby producingneither cross color nor a reduction in vertical resolution.

In the second aspect of the present invention, for example, when thevideo signal for the (n-1)th H is input, the output of the addercorresponds to the color signal for the (n-2)th H, so that the colorcomponent in the Y component is cancelled by the output C. When thevideo for the (n+1)th H is input, the output of the adder is zero andboth the output C and the output Y are zero, thereby producing neithercross color nor lowering in the vertical resolution.

In the third aspect of the present invention, when the video signal forthe (n-1)th H is input, the output of the intermediate value calculatorcorresponds to the color signal for the (n-2)th H, and the colorcomponent of the Y component is cancelled by the output C. When thevideo signal for the (n+1)th H is input, the output of the intermediatevalue calculator is calculated from the output of the first adder andthe output of the second adder and both the output C and the output Ybecome zero.

In this way, according to the present invention, since a nonlinearfilter is used as an operating circuit in a video signal processor, itis possible to greatly reduce the color edging, dot disturbance, crosscolor and reduction in vertical resolution.

The above and other objects, features and advantages of the presentinvention will become clear from the following description of thepreferred embodiments thereof, taken in conjunction with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of a first embodiment of the presentinvention;

FIG. 2 is a block diagram of a second embodiment of the presentinvention;

FIGS. 3 (a) and 3(b) are circuit diagrams of the maximum valuecalculator and the minimum value calculator, respectively, which areused in the first to fourth embodiments of the present invention;

FIG. 4 shows the wave form of each portion of the first and secondembodiments of the present invention;

FIG. 5 shows the wave form of each portion of the first and secondembodiments of the present invention with respect to a different videosignal input;

FIG. 6 is a block diagram of a third embodiment of the presentinvention;

FIG. 7 is a block diagram of a fourth embodiment of the presentinvention;

FIG. 8 shows the wave form of each portion of the third and fourthembodiments of the present invention;

FIG. 9 shows the wave form of each portion of the third and fourthembodiments of the present invention with respect to a different videosignal input;

FIG. 10 is a block diagram of a fifth embodiment of the presentinvention;

FIG. 11 is a block diagram of a sixth embodiment of the presentinvention;

FIG. 12 is a circuit diagram of the intermediate value calculator whichis used in the fifth and sixth embodiments of the present invention;

FIG. 13 shows the wave form of each portion of the fifth and sixthembodiments of the present invention;

FIG. 14 shows the wave form of each portion of the fifth and sixthembodiments of the present invention with respect to a different videosignal input;

FIG. 15 is a block diagram of a conventional video signal processor;

FIG. 16 is a spectrum distribution diagram of the conventional videosignal processor shown in FIG. 15;

FIG. 17 shows the frequency characteristic of the conventional videosignal processor shown in FIG. 15;

FIG. 18 is a wave form of a video signal input;

FIG. 19 shows the wave form of each portion of the conventional videosignal processor;

FIGS. 20A and 20 B show the picture produced by the conventional videosignal processor; and

FIG. 21 shows the wave form of each portion of the conventional videosignal processor with respect to a different video signal input.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 is a block diagram of a YC separating circuit as a firstembodiment of a video signal processor according to the presentinvention. In FIG. 1, the reference numeral 7 represents a 1H-delaycircuit to which a video signal 100 is input. The output of the 1H-delaycircuit 7 is input to a delay circuit 8 and a BPF 9. The output of thedelay circuit 8 is input to a subtractor 10 and the output of the BPF 9is input to a 1H-delay circuit 11 and a phase matching circuit 12.

The video signal 100 is additionally input to a BPF 13, and a firstsignal 101 which is output from the BPF 13 is input to a nonlinearfilter 14. A second signal 102 which is output from the phase matchingcircuit 12 and a third signal 103 which is output from the 1H-delaycircuit 11 are also input to the nonlinear filter 14.

The nonlinear filter 14 is composed of a maximum value calculator 15, aminimum value calculator 16, a double amplifier 17 and a synthesizer 18.The first signal 101 is input to the maximum value calculator 15 and theminimum value calculator 16, and also input to the synthesizer 18 as anaddition signal (positive signal). The second signal 102 which is outputfrom the phase matching circuit 12, and the third signal 103 which isoutput from the 1H-delay circuit 11, as well as the first signal 101,are input to the maximum value calculator 15 and the minimum valuecalculator 16. The output signals 104 and 105 of the maximum valuecalculator 15 and the minimum value calculator 16, respectively, areinput to the synthesizer 18 as subtraction signals (negative signals),and the second signal 102 is input to the synthesizer 18 as an additionsignal through the double amplifier 17. The output of the synthesizer 18is input to a gain adjuster 19, and the output of the gain adjuster 19is output as a C signal and added to the subtractor 10 as a subtractionsignal, the output of the subtractor 10 being output as a Y signal.

FIGS. 3(a) and 3(b) show the concrete circuits of the maximum valuecalculator 15 and the minimum value calculator, respectively.

In FIG. 3(a), the reference numerals 20 to 22 represent NPN transistors,to the respective bases of which the signals 101 to 103 are inputthrough capacitors 23 to 25, respectively. The respective bases areconnected to one end a resistor 29 and one end of a capacitor 30 throughresistors 26 to 28, respectively, and the other ends of the resistor 29and the capacitor 30 are grounded. The collectors of the transistors 20to 22 are connected to the power source Vcc and the emitters aregrounded through a resistor 31. The output thereof is supplied as anoutput signal 104. The power source Vcc is connected to one end of theresistor 29 and one end of the capacitor 30 through a resistor 32.

In FIG. 3(b), the reference numerals 33 to 35 represent PNP transistors,to the respective bases of which the signals 101 to 103 are inputthrough capacitors 36 to 38, respectively. The respective bases areconnected to one end a resistor 42 and one end of a capacitor 43 throughresistors 39 to 41, respectively, and the other ends of the resistor 39and the capacitor 43 are grounded. The emitters thereof are connected toone end of a resistor 42 and one end of the capacitor 43 throughresistors 44 and 45 and also outputs an output signal 108. Thecollectors thereof are grounded.

The operation of this embodiment will now be explained The video signal100 is passed through the BPF 13 and input to the maximum valuecalculator 15 and the minimum value calculator 16 in the nonlinearfilter 14 in the form of the first signal 101 in the frequency band notlower than the frequency band for a color signal. The video signal 100is passed through the 1H-delay circuit 7, the BPF 9 and the phasematching circuit 12 and input to the maximum value calculator 15 and theminimum value calculator 16 in the form of the second signal 102 whichis in the frequency band not lower than the frequency band for a colorsignal and is output after the first signal 101 with a delay of 1H. Theoutput of the BPF 9 is passed through the 1H-delay circuit 11 and inputto the maximum value calculator 15 and the minimum value calculator 16in the form of the third signal 103 which is in the frequency band notlower than the frequency band for a color signal and is output after thefirst signal 101 with a delay of 2H's. That is, the first to thirdsignals 101 to 103 are in the frequency band for a color signal and areconsecutively output with a delay of 1H in series. The phases of thefirst to third signals are matched in the color subcarrier frequencies.The phase matching circuit 12 is an amplifier having a gain of -1 dB,namely, an amplifier for shifting the phase by 180 degrees. This isbecause the color signal is inverted for every H.

The maximum value calculator 15 outputs the maximum value of the firstto third signals 101 to 103 which are input to the bases of thetransistors 20 to 22, respectively, to the emitter as the output signal104. For example, if the signal 101 is the maximum, the transistor 20acts as an emitter follower and the signal 104 having the same amplitudeas the signal 101 is taken out. In an ordinary case, the potential ofthe connecting point of the resistor 32 and the resistor 29 is set atabout Vcc/2. No electric conduction is established between the bases andthe emitters of the transistors other than that having the maximuminput.

The minimum value calculator 16 outputs the minimum value of the firstto third signals 101 to 103 which are input to the bases of thetransistors 39 to 41, respectively, to the emitter as the output signal105 in the same way as the maximum value calculator 15 because the PNPtransistors are adopted as the transistors 39 to 41.

The output signals 104 and 105 of the maximum value calculator 15 andthe minimum value calculator 16 are input to the synthesizer 18 assubtraction signals, and the first signal 101, the third signal 103 andthe doubled second signal, which is obtained by amplifying the secondsignal 102 by the double amplifier 17, are also input to the synthesizer18 as addition signals. The output of the synthesizer 18 is an improvedcolor signal output with a delay of 1H, as will be described later. Itis therefore possible to obtain a luminance signal Y and a color signalC by compounding the video signal output from the 1H-delay circuit 7with a delay of 1H and this color signal by the subtractor 10 in thesame way as a conventional video signal processor.

FIG. 4 shows a wave form of each portion of the embodiment when thevideo signals 100 similar to those for the (n-1)th H, n-th H and (n+1)thH shown in FIG. 18 are input. As shown in FIG. 4, when the video signal100 for the (n-1)th H is input, the first to third signals 101 to 103input to the nonlinear filter 14 have the same phase and same amplitude,so that the outputs 104, 105 of the maximum value calculator 15 and theminimum value calculator 16, respectively, have the same phase and thesame amplitude. Therefore, the output of the synthesizer 18, namely,(the signal 101+the doubled signal 102+signal 103-signal 104-signal 105)has the same phase as the signals 101 to 103 and twice the amplitude ofthe signals 101 to 103. The amplitude of the output of the synthesizer18 is reduced to 1/2 and the phase thereof is inverted by the gainadjuster 19 and is output as the C signal which corresponds to the colorsignal for the (n-2)th H. The color component in the Y signal componentfor the (n-2)th H, which is output from the delay circuit 8, iscancelled by the C signal in the subtractor 10.

When the video signal 100 for the n-th H is input, there is no colorsignal component in the video signal 100, so that only the first signal101 becomes zero. Therefore, the output signal 104 of the maximum valuecalculator 15 is in the form of a positive half wave and the outputsignal 105 of the minimum value calculator 16 is in the form of anegative half wave. As a result, the output of the synthesizer 18 is asignal which has the same phase as the signal 102 and 103 and twice theamplitude thereof. Therefore, the gain adjuster 19 produces the output Cwhich correspond to the signal for the (n-1)th H and the subtractor 10cancels the color component in the Y signal component.

When the video signal for the (n+1)th H is input, only the third signal103 remains as the color signal, and the output signal 104 of themaximum value calculator 15 is in the form of a positive half wave andthe output signal 105 of the minimum value calculator 16 is in the formof a negative half wave. Therefore the output of the synthesizer, (whichis the signal 103-the signal 104-the signal 105) becomes zero. As aresult, there is no output C, and the C signal corresponds to a colorsignal for the n-th H. When the video signal 100 for the (n+2)th H isinput, the nonlinear filter 14 has no input. Hence, there is neitheroutput Y nor output C.

In these operations, since the output Y is obtained from the output ofthe 1H-delay circuit 7 on each line, the line for the output Y agreeswith the line for the output C.

When the output on each line is compared with that in the conventionalfilter shown in FIG. 19, it is observed that the output on the n-th Hbecomes zero in this embodiment, and that the color edging and dotdisturbance have been removed.

The influence on the luminance signal is shown in FIG. 5. It is assumedthat in the picture in which the black bar is sagging and is cut at then-th H, the video signal 100 for the (n+1)th H is input. The thirdsignal 103 generated when the input video signal 100 passes through the1H-delay circuits 7 and 11 has a transient when it passes through theBPF 9. Since the second signal 102 and the first signal 101 are zero,the output signal 104 of the maximum value calculator 15 is the positivetransient of the third signal 103, and the output signal 105 of theminimum value calculator 16 is the negative transient of the thirdsignal 103. The output of the synthesizer 18 is therefore zero, and theoutput C and the output Y contain no color component. In other words,with respect to the signal for the n-th H which is output when the videosignal 100 for the (n+1)th H is input, neither output Y nor output C isgenerated, thereby causing neither cross color nor deterioration in theresolution, unlike in the conventional video signal processor.

FIG. 2 shows a noise filter utilizing horizontal correlation as a secondembodiment of the present invention. In FIG. 2, the reference numeral 46represents an amplitude limiter provided between the gain adjuster 19and the subtractor 10. The output of the amplitude limiter 46 is inputto the subtractor 10 as a subtraction signal. Since the other structureis the same as that of the YC separating circuit shown in FIG. 1, thesame reference numerals are provided for the corresponding elements andexplanation thereof will be omitted.

The operation of the noise filter having the above-described structurewill now be explained. A luminance signal containing noise is input asthe video signal 100. The operation of the noise filter in the flowchart from the video signal 100 to the gain adjuster 19 is the same asthe first embodiment. In this way, a signal corresponding to a colorsignal is output from the gain adjuster 19. Noise signals havingdifferent phases in lines, for example, are output, and the luminancesignals having the same phase are not output for the respective lines.More specifically, when a luminance signal is input, noise having afrequency in the vicinity of (2N+1)/2TH (N: integer) and a smallamplifier is output from the gain adjuster 19 and input to thesubtractor 10 through the amplifier limiter 46. The subtractor 10operates a noise filter so as to cancel the noise in the luminancesignal. An oblique stripe component in the luminance signal can have asimilar frequency, but since the amplitude of the component at a highlevel is not limited by the amplifier limiter 46 and the component isnot cancelled by the subtractor 10, the lowering in the obliqueresolution is prevented.

The noise filter of this embodiment does not cause the lowering in thevertical resolution, as in the first embodiment, thereby eliminating thedefect of the conventional video signal processor.

The synthesizer 18 can carry out the same operation as that in the aboveexplanation if the ratio of the input to the synthesizer 18 is the sameas in the first and second embodiments. For example, if the compoundingpolarities of the synthesizer 18 are changed [so as to have the input ofthe signal 104+the signal 105-(the signal 101+the signal 102×2+thesignal 103)], the gain of the gain adjuster 10 is changed to 1/2 dB. Ifall the inputs to the synthesizer 18 are reduced to 1/2, the gain of thegain adjuster 19 is changed to -1 dB. In FIG. 1, the output of thesynthesizer 18 may be utilized directly as a color signal. Although theoutput of the synthesizer 18 has a different phase and a differentamplitude from those of the color signal component of the video signal100, since it can be used as a color signal as it is, the gain adjuster19 is not particularly required.

FIG. 6 shows a YC separating circuit as a third embodiment of thepresent invention. This embodiment has the same structure as the firstembodiment shown in FIG. 1 except for a nonlinear filter 47. Thenonlinear filter 47 has a first synthesizer 48 for compounding theantiphase first signal 101, the doubled second signal 102 which isamplified by a double amplifier 49 and the third signal 103, and theoutput 50 of the first synthesizer 48 is input to the maximum valuecalculator 15 and the minimum value calculator 16. The reference numeral51 represents a second synthesizer for adding the first signal 101 andthe third signal 103 and inputting the output 52 to the maximum valuecalculator 15 and the minimum value calculator 16. The reference numeral53 represents a third synthesizer for compounding the first signal 101,the doubled second signal 102 and the antiphase third signal 103 andinputting the output 54 to the maximum value calculator 15 and theminimum value calculator 16. The maximum value calculator 15 and theminimum value calculator 16 are the same circuit as in the first andsecond embodiments. The outputs of the maximum value calculator 15 andthe minimum value calculator 16 are added by an adder 55 and the sum isinput to the gain adjuster 19.

The operation of the third embodiment will now be explained. FIG. 8shows a wave form of each portion of the embodiment when the videosignals 100 for the (n-1)th H, n-th H and (n+1)th H are input. When thevideo signal 100 for the (n-1)th H is input, the first to third signals101 to 103 input to the nonlinear filter 47 have the same phase and thesame amplitude, so that the outputs 50, 52 and 54 of the first, secondand third synthesizers 48, 51 and 53, respectively, have the same phaseas the signals 101 to 103 and twice the amplitude thereof. The outputsof the maximum value calculator 15 and the minimum value calculator 16,respectively, also have the same phase as the signals 101 to 103 andtwice the amplitude thereof. The output of the adder 55 is multiplied by-1/4 and the thus-obtained output C corresponds to the color signal forthe (n-2)th H. The color component in the video signal is cancelled bythe output C in the subtractor 10 to obtain the Y signal.

When the video signal 100 for the n-th H is input, there is no colorsignal component in the video signal, so that only the first signal 101becomes zero. That is, the outputs 52 and 54 of the synthesizers 51 and53, respectively, having the same phase and the same amplitude as thesecond and the third signals 102 and 103, and the output 50 of thesynthesizer 49 having the same phase as the second and third signals 102and 103 and three times the amplitude thereof are obtained. Therefore,when the outputs of the maximum value calculator 15 and the minimumvalue calculator 16 are compounded by the adder 55, a signal having thesame phase as the signals 102 and 103 and four times the amplitudethereof is obtained. The output C obtained by multiplying the output ofthe adder 55 by -1/4 corresponds to the color signal for the (n-1)th H.The color component in the video signal is cancelled by the output C inthe subtractor 10 to obtain the Y signal.

When the video signal 100 for the (n+1)th H is input, only the thirdsignal 103 remains. The outputs of the synthesizers 48 and 51 have thesame phase and the same amplitude as the third signal 103, and theoutput 54 of the synthesizer 53 has the inverted phase and the sameamplitude as the third signal 103. Therefore, when the maximum value andthe minimum value thereof are added, the sum is zero. In other words,the output C is a color signal corresponding to a color signal for then-th H. When the video signal 100 for the (n+2)th H is input, thenonlinear filter 47 has no input and, hence, there is neither output Ynor output C. In these operations, since the output Y is obtained fromthe output of the 1H-delay circuit 7 on each line, the line for theoutput Y agrees with the line for the output C.

When the output on each line in the third embodiment is compared withthat in the conventional filter shown in FIG. 19, it is observed thatthe output on the n-th H becomes zero in this embodiment, and that thecolor edging and dot disturbance have been removed.

The influence on the luminance signal is shown in FIG. 9. It is assumedthat in the picture in which the black bar is sagging and is cut at then-th H, the video signal 100 for the (n+1)th H is input-in the same wayas in FIG. 5. The third signal 103 generated when the video signal 100input for the (n-1)th H passes through the 1H-delay circuits 7 and 11has a transient when it passes through the BPF 9. Since the secondsignal 102 and the first signal 101 are zero, the output of the adder 55is zero and both the output C and the output Y are zero in the same wayas when the video signal 100 for the (n+1)th H is input in FIG. 8. Thus,there is neither cross color nor deterioration in the resolution as inthe first embodiment.

FIG. 7 shows a noise filter as a fourth embodiment of the presentinvention. In FIG. 7, the reference numeral 56 represents an amplitudelimiter for inputting the output of the gain adjuster 19 and outputtingthe output of the gain adjuster 19 to the subtractor 10 as a subtractionsignal. The other structure is the same as that of the third embodiment.

The operation of the noise filter having the above-described structurewill now be explained. A luminance signal is input as the video signal100, and the output of the adder 55 is output from the gain adjuster 19in the form of a signal corresponding to a color signal in the same wayas in the third embodiment. Therefore, in the fourth embodiment, thereis no lowering in the vertical resolution as in the noise filter of thesecond embodiment.

The synthesizers 48, 51 and 53 can-carry out the same operation as thosein the above explanation if the ratio of the input to the synthesizers48, 51 and 53 are substantially the same as in the third and fourthembodiments. For example, if the compounding polarities of thesynthesizers 48, 51 and 53 are changed with each other, the gain of thegain adjuster 10 is changed to 1/4 dB. If all the inputs to thesynthesizers 48, 51 and 53 are reduced to 1/4, the gain of the gainadjuster 19 is changed to -1 dB. Although the output of the adder 55 hasa different phase and a different amplitude from those of the colorsignal component of the video signal 100, since it can be used as acolor signal as it is, the gain adjuster 19 is not particularlyrequired.

FIG. 10 shows a YC separating circuit as a fifth embodiment of thepresent invention. In FIG. 10, the reference numeral 57 represents anonlinear filter composed of the following elements. The referencenumeral 58 represents an adder for adding the first signal 101 and thesecond signal 102, 59 an adder for adding the second signal 102 and thethird signal 103. The outputs 60 and 61 of these adders 58 and 59,respectively, are input to an intermediate value calculator 62. To theintermediate value calculator 62 is input the output 64 which isobtained by doubling the second signal 102 by a double amplifier 63. Theoutput of the intermediate value calculator 62 is input to the gainadjuster 19. The other structure is the same as those of the first tofourth embodiments.

FIG. 12 shows the concrete circuit of the intermediate value calculator62. In FIG. 12, the reference numerals 65, 66 and 67 each represent apair of NPN transistors with the emitters connected to each other. Theinputs 60 and 61 are connected to the bases of the transistors 65, theinputs 61 and 64 are connected to the bases of the transistors 66, andthe inputs 64 and 60 are connected to the bases of the transistors 67.The emitters of the transistors 65, 66 and 67 are connected to the basesof PNP transistors, 68, 69 and 70, respectively, and the emitters ofthese PNP transistors, 68, 69 and 70 are connected to the power sourceVcc through a resistor 71 and the emitter currents are taken out as anoutput. The collectors of these transistors 68, 69 and 70 are grounded.The reference numerals 72, 73 and 74 represent capacitors connectedbetween the inputs 60, 61 and 64 and the transistors 65 to 67,respectively, and 75 to 77 represent resistors provided between therespective connecting points of the capacitors 72 to 74 and the bases ofthe transistors 65 to 67 and the connecting points of the resistors 78and 79 which are connected between the power source Vcc and thegrounding. The reference numeral 80 to 82 represent resistors providedbetween the respective emitters of the transistors 65 to 67 and thegrounding, and 83 represents a capacitor connected between theconnecting points of the resistors 78 and 79 and ground.

The operation of the YC separating circuit having the above-describedstructure will be explained. As to the first to third signals 101 to 103input to the nonlinear filter 57, the first and second signals 101 and102 are added by the adder 58 and the second and third signals 102 and103 are added by the adder 59. These outputs 60 and 61 are input to theintermediate value calculator 62. The second signal 102 is amplified bythe double amplifier 63 and the output 64 is input to the intermediatevalue calculator 62. In the intermediate value calculator 62, the pairsof transistors 65 to 67 output the signals 60, 61 and 64, respectively,having the larger value which are input to the respective bases.Therefore, the minimum value of the signals 60, 61 and 64 are notcontained in the outputs of the transistors 65 to 67. Since thetransistors 68 to 70 output the minimum value of the signals output bythe transistors 65 to 67, an intermediate value is output inconsequence. The intermediate value is an improved color signal which isoutput by a delay of 1H, as will be explained in the following.Therefore, the luminance signal Y and the color signal C are obtained inthe same way as in the first and third embodiments.

FIG. 13 shows a wave form of each portion of the embodiment when thevideo signals 100 for the (n-1)th H, n-th H and (n+1)th H are input.When the video signal 100 for the (n-1)th H is input, the three signalsinput to the nonlinear filter 57 have the same phase and the sameamplitude, so that all the inputs 60, 61 and 64 to the intermediatevalue calculator 62 have the same phase and the same amplitude. Theoutputs C corresponding to the color signal for the (n-2)th H istherefore obtained. The color component in the output Y is cancelled bythe output C in the subtractor 10. When the video signal 100 for then-th H is input, there is no color signal component in the video signal,so that only the first signal 101 becomes zero. Therefore, the input 60is half as large as the other inputs, and an intermediate value iscalculated from the inputs 64 and 61. As a result, the output Ccorresponding to the color signal for the (n-1)th H is obtained. Thecolor component in the output Y is cancelled by the output C. When thevideo signal 100 for the (n+1)th H is input, only the third signal 103remains as the input 61. Since both the inputs 60 and 64 are zero, anintermediate value is calculated from these inputs 60 and 64. As aresult, there is no output C, which corresponds to the color signal forthe n-th H. When the video signal 100 for the (n+2)th H is input, thenonlinear filter 57 has no input and, hence, there is neither output Ynor output C. In these operations, since the output Y is obtained fromthe output of the 1H-delay circuit 7 on each line, the line for theoutput Y agrees with the line for the output C.

When the output on each line in the fifth embodiment is compared withthat in the conventional filter shown in FIG. 19, it is observed thatthe output on the n-th H becomes zero in this embodiment, and that thecolor edging and dot disturbance have been removed.

The influence on the luminance signal is shown in FIG. 14. It is assumedthat in the picture in which the black bar is sagging and is cut at then-th H, the video signal 100 for the (n+1)th H is input. The thirdsignal 103 generated when the video signal 100 input for the (n-1)th Hpasses through the 1H-delay circuits 7 and 11 has a transient when itpasses through the BPF 9. Since the second signal 102 and the firstsignal 101 are zero, in the intermediate value calculator 62, the input61 is equal to the third signal 102, and the other inputs are zero.Therefore, the output of the intermediate value calculator 62 iscalculated from the inputs 60 and the input 64, and both the output Cand the output Y are zero. In other words, with respect to the signalfor the n-th H, neither the output Y nor the output C is generated,thereby causing neither cross color nor deterioration in the verticalresolution.

FIG. 11 shows a noise filter as a sixth embodiment of the presentinvention. In FIG. 11, the reference numeral 84 represents an amplitudelimiter provided between the gain adjuster 19 and the subtractor 10 asin the second and fourth embodiments. The other structure is the same asthe fifth embodiment.

The noise filter having the above-described structure carries out thesame operation as the second and fourth embodiments. Therefore, thenoise filter of this embodiment is also effective for causing reductionvertical resolution.

In the fifth and sixth embodiment, the inputs 60, 61 and 64 of theintermediate value calculator 62 are (the first signal 101+the secondsignal 102), (the doubled second signal 102) and (the second signal102+the third signal 103), respectively. However, since the object ofthe intermediate value calculator 62 is to calculate an intermediatevalue, these inputs may be any other values so long as the ratio issubstantially constant. For example, the inputs 60, 61 and 64 may be(the average of the first signal 101 and the second signal), (the secondsignal 102) and (the average of the second signal 102 and the thirdsignal 103). In this case, since the output of the intermediate valuecalculator 62 is reduced to 1/2, the gain of the gain adjuster 19 ischanged to -1 dB. Although the output of the intermediate valuecalculator 62 has a different phase and a different amplitude from thatof the color signal component of the video signal 100, since the outputcan be used as a color signal as it is, the video signal processor maydispense with the gain adjuster 19.

The range of application of each element in each of these embodimentswill now be explained. The phase matching circuit 12 is an amplifier forshifting the phase by 180 degrees so as to match the phases of the firstto third signal 101 to 103, as described above. Since the color signaldelayed by 1H has an inverted phase, at least this function isnecessary. However, it is said that the critical phase differencedetectable with human eyes is as small as 2 degrees. Therefore, the1H-delay circuits 7, 11, the BPF's 9, 13, etc. may have respectivefunctions of matching the phases of the three signals. Alternatively,the BPF 9 may also have the function of matching phases. Further the1H-delay circuit 11 for matching the phase of the third signal 103 mayalso have the function of inverting the phase. Furthermore, in the thirdand fourth embodiments, it is possible to unite the phase matchingcircuit 12 and the double amplifier 17 into one body, as an amplifierhaving a gain of -2 dB.

The 1H-delay circuits 7 and 11, which are required for generating thesecond and third signals 102 and 103, may be effectively utilized fordelaying signals by any other time. For example, in the PAL system, inwhich the phases of a color burst signal and a color signal are invertedfor every 2H's, a YC separating circuit of the PAL system can berealized by using 2H-delay circuits in place of the 1H-delay circuits 7and 11. Furthermore, in the NTSC system, in which the phases of a colorburst signal and a color signal are inverted in every frame, a YCcircuit may also be realized by using 525H-delay circuits in place ofthe 1H-delay circuits 7 and 11. It is also possible to realize a digitalYC separating circuit by using delay circuits having a memory as thesedelay circuits, digital computers as the adders and the calculators, anddigital signals as the signals.

The BPF's 9 and 13 are filters for transmitting a color signal, asexplained in the related art. The BPF's 9 and 13 in the presentinvention are used so as to suppress a lower frequency band which isunnecessary for calculating an intermediate value of higher frequencyband components of a color signal or a luminance signal by the nonlinearfilters 14, 47 and 57. For example, if it is assumed that the BPF's 9and 13 transmit a direct current, the nonlinear filters 14, 47 and 57calculate an intermediate value including the direct current, so that itis impossible to calculate an intermediate value of higher frequencycomponents of a color signal or a luminance signal and, hence, to outputa desire color signal or unrelated luminance signal. In order to cancelthe direct current, the band of frequencies which th BPF's 9 and 13transmit is not limited to 3.58 MH_(z) ±500 KH_(z) and may be broader.For example, the BPF's 9 and 13 may be high-pass filters fortransmitting frequencies of not less than 2MH_(z).

As described above, the main outputs obtained by processing signals inthe above-described embodiments are color signals or unrelated luminancesignals with the lower frequency band suppressed which are obtained fromthe outputs of the nonlinear filters 14, 47 and 57. If only thesesignals are desired, the auxiliary delay circuit 8 and subtractor 10 forobtaining a Y signal are unnecessary. For example, the nonlinear filter14, 47 and 57 may be utilized as a filter for cancelling the crosstalkcomponent in a color signal, thereby eliminating the phenomenon of coloredging, as explained in the related art.

These embodiments have the following effects as well as theabove-described fundamental effects. In the first to fourth embodiments,signals are nonlinearly processed in the circuits shown in FIGS. 3(a)and 3(b) so as to obtain a color signal. For the purpose of switching,an input of not less than 100 mVp-p is necessary. If the input is assmall as about 20 mVp-p, the output becomes the sum of the inputs 101,102 and 103 and an adequate color signal separating operation is notexpected. If such nonlinear processing is carried out in series atmulti-stages, such conveniences are multiplied. In these embodiments,however, since the nonlinear processing is carried out at a singlestage, the inconvenience is limited to the minimum and the inputamplitude is also limited to the minimum.

In the switching circuits shown in FIG. 3 (a) and 3 (b) , the delay timeis in the order of 10 ns. This is 13 degrees in terms of the phase of acolor signal, which greatly exceeds the critical phase differencedetectable with human eyes. Therefore, in the system in which a signalwhich passes the switching circuit and a signal which does not pass theswitching circuit are compounded, a delay compensating circuit formatching the delay times of these signals is required. In the third andfourth embodiments, however, since the adder 55 compounds the outputs ofthe switching circuits, there is no color edging and no delaycompensation is required, thereby enabling reduction in cost.

In the fifth and sixth embodiments, addition and subtraction of signalsfor obtaining a color signal is carried out at the stage preceding theintermediate value calculator 62, and no addition or subtraction iscarried out between the signal which passes the intermediate valuecalculator 62 and a signal which does not pass the intermediate valuecalculator 62. If the latter addition or subtraction is carried out, theswitching circuit shown in FIG. 12 causes delay in the order of 10 ns,so that a delay compensating circuit for matching the delay times beforethe addition or subtraction is necessary. That is, since 10 ns is about13 degrees in terms of the phase of a color signal, which greatlyexceeds the critical phase detectable by human eyes, therebynecessitating compensation for the delay. In these embodiments, however,such addition or subtraction is not carried out, so that compensationfor the delay to the intermediate value calculator 62 is unnecessary.Thus, there is no deviation of the phase of a color signal, and it ispossible to separate a color signal at a low cost.

While there has been described what are at present considered to bepreferred embodiments of the invention, it will be understood thatvarious modifications may be made thereto, and it is intended that theappended claims cover all such modifications as fall within the truespirit and scope of the invention.

What is claimed is:
 1. A video signal processor for use in a televisionset for processing a video signal, input in horizontal line periods,said video signal processor comprising:first and second delay circuits,said first delay circuit for delaying said video signal input thereto bya horizontal line period and said second delay circuit for furtherdelaying said delayed input video signal by a second horizontal lineperiod so as to produce a first delay signal and a second delay signal,respectively; signal processing means for receiving said input videosignal, said first delay signal and said second delay signal and forproducing and outputting a separated signal component of the input videosignal, the signal processing means including, a first synthesizer forcompounding an antiphase version of the input video signal, said firstdelay signal and said second delay signal and for outputting a firstoutput signal, a second synthesizer for compounding said input videosignal and said second delay signal and for outputting a second outputsignal, a third synthesizer for compounding said input video signal, adoubled version of the first delay signal and an antiphase version ofthe second delay signal and for outputting a third output signal, amaximum value calculator for comparing the first, second and thirdoutput signals and outputting a maximum value, a minimum valuecalculator for comparing the first, second and third output signals andoutputting a minimum value, and an adder for adding the output of saidmaximum value calculator and the output of said minimum value calculatorand for outputting the separated signal component to a separator; phaseshifting means for shifting a phase of said first delay signal to aphase of the separated signal component output from the signalprocessing means; and the separator for removing the separated signalcomponent output from the signal processing means from said phaseshifted first delay signal to remove the separated signal component fromthe input video signal.
 2. The video signal processor of claim 1,wherein said first delay circuit and said second delay circuit areconnected in series, said first delay circuit outputting said firstdelay signal, and said second delay circuit outputting said second delaysignal.
 3. The video signal processor of claim 1, further comprising afiltering means for substantially suppressing lower frequency bands ofsaid input video signal and said first delay signal.
 4. The video signalprocessor of claim 3, wherein said filtering means includes,a firstfilter for suppressing a lower frequency band of said input video signalprior to input to said first, second and third synthesizers; and asecond filter for suppressing a lower frequency band of said first delaysignal.
 5. The video signal processor of claim 1, furthercomprising:phase inverting means for inverting the phase of said firstdelay signal prior to input to said first and third synthesizers; and anamplitude adjusting means for adjusting the amplitude of said phaseinverted first delay signal.
 6. The video signal processor of claim 5,wherein said phase shifting means is a third delay circuit for delayingsaid first delay signal, and said amplitude adjusting means is a gainadjuster for multiplying said phase inverted first delay signal by
 2. 7.The video signal processor of claim 1, further comprising phaseinverting means for inverting the separated signal component output fromthe adder, prior to input to the separator.
 8. The video signalprocessor of claim 1, wherein said input video signal includes a colorsignal and a luminance signal, said separated signal component outputfrom said adder is a color signal, and an output of said separator is aluminance signal.
 9. The video signal processor of claim 1, wherein saidinput video signal is a luminance signal, said separated signalcomponent output from said adder is a noise component, and saidseparator separates said noise component from said luminance signal.